Life Histories of Some Common Vernal Pool Organisms

Wood Frog * Spotted Salamander * Fairy Shrimp
Spring Peeper * Green Frog * Water Beetle * Fingernail Clam

Wood Frog (Rana sylvatica)

Wood frogs are common inhabitants of vernal pools in the Deerfield River watershed. They range from 2-3 inches in length, and vary in color from dark brown to tan to shades of pink. Males are usually darker in color than females. Both sexes have a dark mask running through and beyond their eye.  The best time to observe wood frogs is in early spring when they return to vernal pools to breed. In the watershed, choruses of males have been heard from late March to late April. Listen for wood frogs on rainy nights in early spring when the snow has begun to melt.

Additional natural history facts:

adult wood frog Adult wood frog
wood frog eggs
Newly laid wood frog egg masses: note the small black eggs inside the transparent jelly-like matrix

wood frog egg mass
Wood frog egg masses clustered in one section of pool
The green color is from an alga that colonizes the egg masses. The alga does not harm the eggs

Spotted Salamander (Ambystoma maculatum)

This salamander is large and chunky, ranging from 4.5 and 9.0 inches long. Its bright yellow spots scattered on a black to dark gray background make it easy to identify. Spotted salamanders are rarely seen outside the breeding season, which takes place in late winter or early spring when adults leave their underground burrows and travel to vernal pools. During studies in the Deerfield River watershed, adults were rarely observed in pools.

Additional natural history facts:

spotted salamander

Adult spotted salamanders found crossing road in spring in western Massachusetts

salamander egg masses

Spotted salamander egg mass: note that each egg mass is surrounded by a jelly-like matrix

young salamander

Young spotted salamander larva
Note the feather-like gills around the head which distinguishes it from wood frog tadpoles

older spotted salamander

Spotted salamander larva about 1.5 inches long
It is about 60 days old and will be ready to leave pool between 70-100 days after hatching

Fairy Shrimp (Genus Eubranchipus spp.)

Fairy shrimp are small crustaceans (0.5-1.5 inches long) that require fishless pools to breed successfully. In early spring they can be found floating on or near the surface and look superficially like small green or orange shrimp. The fairy shrimp found in our area belong to the genus Eubranchipus. Fairy shrimp hatch from eggs that lie on the pool bottom until the pool fills with water. They feed while laying or swimming on their backs, filtering various small microorganisms, algae, and bacteria. Fairy shrimp are found in pools in late winter and early spring, before water temperatures reach between 68 and 72 degrees F. It is likely that fairy shrimp have evolved to complete their life cycle before most predators become active in the pool. Their distribution at pools is not predictable and they may be observed in some pools every year, or be found sporadically in others.

The Vernal Pool Association website has wonderful photographs of a variety of invertebrates, including fairy shrimp. Go to their image gallery to see photographs of many vernal pool organisms:

Other animals that may be found in vernal pools but are not dependent on them to breed successfully:

Spring Peeper (Pseudacris crucifer)

Spring peepers are familiar to most people because of their loud, deafening, high-pitched choruses heard during spring throughout New England. They are small frogs, about an inch long, with a dark X on their back. The color of adults ranges from light to dark brown; some individuals may be reddish in color. Although peepers will breed in vernal pools, they prefer  those that hold water for longer periods, at least 9 months. Peepers have an extended breeding season and may remain at pools from March to May. These frogs may be heard calling during the fall in woodlands throughout the Deerfield River watershed.

:spring peeper
Adult spring peeper observed crossing the road in western Massachusetts

Green Frog (Rana clamitans)

Green frogs are one of the watershed’s most common frogs and are found in a variety of wetlands, from rivers and streams to vernal pools and marshes. Their color is variable, primarily green but also brown, with spots on their legs. Green frogs are large – from 2.5 to 4.0 inches long. Their call sounds like the twang of a guitar string. Green frogs are usually found in vernal pools that hold water throughout the summer or that are semipermanent (e.g., hold water year- long most years). These frogs prey upon flies, beetles, grasshoppers, spiders, and other frogs.  

green frog
Adult green frog: distinguished from the bullfrog by the two ridges that run along its back

Water Beetles (Order Coleoptera)

This large and diverse group of beetles is an important component of the vernal pool community. Adults and larvae from many families may be found in pools.

water beetle

Adult water beetle

Fingernail Clams (Phylum Mollusca, Class Bivalvia)

Fingernail clams are small bivalves with a shell length of less than 0.5 inches. Depending on the species, shell color ranges from off-white to light brown, or shades of gray. Several species may be found in vernal pools.

See a fingernail clam photo